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A Topical Approach to
Life-Span Development 6e
• Journal entry prompt: What physical changes
can you expect as you age? How will your
body change? How will your brain change?
How will your sleep change? How long can
you expect to live?
Chapter Three:
Physical Development
and Biological Aging
John W. Santrock
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Height and Weight
in Infancy and Childhood
Body Growth and Change
• Patterns of growth
Rapid growth in height and weight
– Cephalocaudal pattern – From top (head) and
gradual to bottom
– Proximodistal pattern – Center of body outward
to extremities
Infancy
Triple birth weight by 1 year
½ adult height, 20% adult weight by age 2
Growth slows, patterns vary individually
Early
Childhood
Girls slightly smaller and lighter
Girls gain fat, boys gain muscle
Slower, consistent growth
Middle and
Muscle mass and strength increase
Late Childhood
Body proportions change
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Figure 3.1 - Changes in Proportions of
the Human Body During Growth
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Body Growth and Change
• Puberty (early adolescence)
– Period of rapid physical and hormonal changes
– Physical changes; growth spurt (earlier for girls)
• Girls – Menarche, hips widen, breasts enlarge, body hair
– Onset for most: 9 to 15 years of age
• Boys – First ejaculation, increase in penis and testicle
size, voice changes, grow taller, body hair
– Onset for most: 10 to 17 years of age
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© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Body Growth and Change
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Body Growth and Change
• Puberty
– Hormonal changes
• Early adulthood
• Hormones -- Powerful chemicals from endocrine glands
– Height is constant
– Many reach peak of muscle tone and strength in
late teens and twenties
– Peak in joint functions in twenties
– Decline in the thirties
– Hormones increase dramatically in adolescence
• Both testosterone and estradiol present in both boys and
girls
• Testosterone – Voice change, genital growth
– Dominates male changes
• Estradiol – Estrogen for breast growth
– Dominates female changes
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Body Growth and Change
Body Growth and Change
• Middle adulthood
• Middle adulthood
– Physical appearance
– Strength, joints, and bones
• Loss of height (more for women), weight gain
• Skin wrinkles, sagging, aging spots appear in 40s or 50s
• Hair thins and grays
• Sarcopenia – age-related muscle mass and strength loss
• 1% to 2% muscle loss per year after age 50
• Bone loss
– Cardiovascular system and lungs
• HDL and LDL cholesterol, clogged arteries
• Hypertension: blood pressure increases
• Decreased lung capacity after age 55
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Figure 3.4 - Lung Capacity, Smoking and
Age
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Body Growth and Change
• Middle adulthood
– Sexuality changes
• Climacteric — fertility declines
• Menopause — menstrual periods ceases
– Dramatic decline of estrogen; not a negative
experience for most women
– Males do not lose fertility
• Modest decline in sexual hormone level and activity
• Testosterone production begins to decline
• Decline in sperm count
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Body Growth and Change
The Brain
• Late adulthood
• Brain physiology
– Physical appearance more pronounced
– Structure and function
• Facial wrinkles, age spots
• Weight loss due to muscle loss after age 60; decreased
by exercise and weight lifting
• 2 halves, or hemisphere
• Forebrain, top of the brain, its outer layer of cells is the
“cerebral cortex”
• Each hemisphere of cortex has four lobes
– Frontal, occipital, temporal, parietal lobes
– Circulatory system
• Increased blood pressure, linked to chronic conditions
and longevity
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Figure 3.6 - The Brain’s Four Lobes
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Functions of Lobes of the Cortex
Frontal
Involved in voluntary movement, thinking,
personality, and intentionality or purpose
Occipital
Function in vision
Parietal
Roles in registering spatial location,
attention, and motor control
Temporal
Active role in hearing, language
processing, and memory
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© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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The Brain
• Brain physiology
Deeper in brain:
Hypothalamus, pituitary
gland, amygdala
(emotion), hippocampus
(memory and emotion)
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– Neurons: Nerve cells handling information
processing at the cellular level
• Axon, sends electrical signals away from the cell body
• dendrites, the neuron’s bushy, branching extensions that
receive messages
• Synapses, the junction between the axon tip of the
sending neuron and the dendrite or cell body of the
receiving neuron.
• Neurotransmitters: chemicals released into synapses
• Myelin sheath and myelination
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The Brain
Figure 3.7 - The Neuron
• Infancy
– Shaken Baby Syndrome
– Dramatic increases of myelin sheath and neural
connections
– Blooming and pruning of connections in brain
– Brain areas do not mature uniformly; skills
affected by myelination and interconnections
http://youtu.be/FR4S1BqdFG4
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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The Brain
Figure 3.12 - Dendritic Spreading
• Childhood
– The brain and head grow more rapidly than any
other part of the body — growth curves
– Some brain size increase due to myelination and
number and size of dendrites
– Greatest anatomical brain increases from ages 3
to 15 years; distinct bursts of growth
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Figure 3.14 - Growth Curves for Head and
Brain and for Height and Weight
The Brain
• Adolescence
– Brain continues growth
• Corpus callosum (connects two hemisphere) – Axon
fibers thicken, improves information processing
• Prefrontal cortex – Increased reasoning, decision
making, self-control
• Amygdala – Seat of emotions, matures earlier
– Positive link between volume of the amygdala and
duration of aggressive behavior toward parents
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© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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The Brain
The Brain
• Adulthood and aging
–
–
–
–
• The adapting brain
– Exercise and activities influence development
Brain loss: 5-10% of weight in ages 20 to 90
Dendrites decrease; myelin sheath damage
Shrinkage is not uniform; most in prefrontal cortex
General slowing of brain and spinal cord function
• High levels of aerobic fitness were linked with greater
volume in the hippocampus
– Remarkable repair capability
• Neurogenesis: New cells generated
• Dendrite growth; “rewiring” to compensate loss
• Begins in middle age, accelerates with age
– Reductions in neurotransmitters
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Figure 3.19 - Sleep Across the Human
Life Span
Sleep
• Infancy
– Newborns average 16-17 hours a day
– Varied patterns; Most common problem – Night
waking
• More REM sleep than any other time of life
– As infant, half of sleep pattern; begins sleep cycle
• May provide self-stimulation
• Cannot determine if infants dream like adults
– As adult, REM is 20% of sleep pattern; onset 1
hour after non-REM
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© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Sleep
• SIDS
–
–
–
–
Sleep
• SIDS
Infants stop breathing; most die suddenly in night
Highest cause of infant death in United States
Highest risk: Ages 2 to 4 months
Best prevention: Infant sleeps on its back (prone)
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– Risk factors:
•
•
•
•
•
No pacifier, soft bedding, no fan in room
Low-birth weight, sleep apnea, lower SES
Sleeping on stomach or side
Passive exposure to cigarette smoke
Another sibling died of SIDS, abnormal brain stem
functioning
• Higher for African American, Eskimo infants
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Sleep
Sleep
• Childhood
– Recommended: 11 to 13 hours each night
– Sleep problems
• Adolescence
– Inadequate sleep patterns (less than 8 hrs a day)
• Inadequate sleep linked to depression, school problems,
disagreeable families, living in unsafe neighborhoods,
father in poor health
• Alcohol use problems in adolescence and early
adulthood
• an indicator of attention problems
• Emotion security in parent-child and marital relationships
when children were in the third grade predicted fewer
sleep problems when they reached the fifth grade
• Linked to fatigue, moodiness, depression, more caffeine
beverage use, falling asleep in school
– Sleep was 9½ hours when given the opportunity
– Sleep debt: Try to make up lost sleep on weekend
– Older adolescents vs. younger adolescents
• melatonin causes later waking and going to sleep in
older adolescents
• Starting school later would decrease absences
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Sleep
Sleep
• Adolescence
• Adulthood and aging
– Sleep deprivation and school performance
•
•
•
•
•
•
– Many are sleep deprived (less than 7 hrs a day)
• Work, school, social, or family obligations
More reported illnesses and absences
More depressed, lower self-esteem
Ineffective stress management
Less exercise, unhealthy diet
Grogginess, less attentive, poor test scores
Discipline problems
– Middle age may bring sleep problems
• Wakeful periods at night, less deep sleep
– Many older adults go to bed and wake up earlier,
– Insomnia increases in late adulthood
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
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Longevity
Longevity
• Life span: Upper boundary of life, maximum
number of years an individual can live; about
120 years of age
• Life expectancy: Number of years that an
average person born in a particular year will
probably live
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• Life expectancy
– Highest in Japan – 82 years
– Racial and gender differences in the U.S.
• Highest for Non-Latino Whites – 78.4 years
• African Americans – 73.6 years
• Females have higher expectancy than males
– African American females – 76.8
– African American males – 70.0
– White females – 80.8
– White males – 75.9
– Begins in mid-30s, gap increases with age
– Male lifestyle associated with more risks, biological
factors
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Longevity
• Centenarians
– Numbers increasing
• More women than men;
– Influenced by:
• Biology, heredity, family history, coping ability
• Health (weight, diet, smoking, exercise)
• Education, personality, lifestyle
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